Pilot burner



July 28, 1970 w. R DU N. 3,521,982

PILOT BURNER Filed Nov. 22, 1968 '3 FIG 3 I 29 25 FIG. 4 Y

INVENTOR. WILLIAM R. DUNN ATTORNEX United States Patent 3,521,982 PILOT BURNER William R. Dunn, Los Angeles, Calif., assignor to Honeywell Inc., Minneapolis, Minn., a corporation of Delaware Filed Nov. 22, 1968, Ser. No. 778,03

Int. Cl. F23n /10- US. Cl. 431-80 6 Claims ABSTRACT OF THE DISCLOSURE A pilot burner-flame sensor combination wherein the pilot burner has body and head configurations that divides a burner flame into two distinct flames, one for igniting a main burner and the other for heating a flame sensor in the form of a thermocouple. The outlets of the burner have baffies that cause substantially all of the gas and air mixture and, therefore the flame supported thereby, to flow in the direction of the main burner when the gas pressure becomes so low as to not normally provide a suitable flame for igniting the main burner.

BRIEF SUMMARY OF THE INVENTION A pilot burner for igniting a main burner wherein a burner body has a throat construction that cooperates with a target flame divider to provide an igniting flame and a flame sensor flame, the flame sensor flame extenguishing before the igniting flame reduces to a size incapable of igniting a main burner, when the gas pressure falls below a certain level.

DESCRIPTION OF THE DRAWING FIG. 1 of the drawing shows a side elevational View of the invention with a portion thereof broken away;

FIG. 2 is an end elevational view of the invention with a portion of the flame sensor broken away;

FIG. 3 is a plan view of the invention with the flame sensor removed therefrom, taken along line 3-3 of FIG. 1;

FIG. 4 is a cross-sectional view of the invention taken along the line 44 of FIG. 1;

FIG. 5 is a cross-sectional view taken along line 55 of FIG. 1;

FIG. 6 is a cross-sectional view taken along line 6-6 of FIG. 2;

FIG. 7 is a plan view of the pilot burner head and sensor showing the flame pattern of the burner at normal and higher gas pressures; and

FIG. 8 is a plan view of the burner head and sensor showing the flame pattern at a gas pressure below which it would be unsafe to have a flame proving signal from the flame sensor.

DETAILED DESCRIPTION OF THE INVENTION The reference numeral 11 generally designates the entire pilot burner, with the reference numeral 12 designating a formed sheet of metal providing one-half of the burner body and the reference numeral 13 designating a second formed sheet of metal constituting the other half of the burner body. The two halves are spot welded together at spaced points. Large diameter portions 14 and 15 provide a gas chamber therebetween into which an orifice member 16 directs gas from a supply pipe 17, in a conventional manner. The pipe 17 is held in the burner body by means of an annular nut 18 screw threaded into an enlarged portion of the gas chamber, with a compression washer 19 gripping the outside of the supply pipe and bearing against the lower end of the orifice member 16, to hold all of the parts in gas-tight assembled relationship. A narrowed or 3,521,982 Patented July 28, 1970 ice flattened extension 20-21 of the chamber formed between the two plates has one edge 20a thereof extending generally parallel to the axis of the chamber 14-15 and a second edge 20b extending diagonally upwardly and outwardly to the top of the burner body. The upper end of the flattened portion 20 is beveled inwardly at 20c to the plane of the peripheral edge of the metal sheet 12. This provides a generally flattened outlet at the top of the burner body which is substantially rectangular in shape up to the edge 20d of the unreduced portion of the portion 20 that reaches the top of the burner. The unreduced portion, with the opposed corresponding portion in the metal sheet 13, provides a wider and generally square opening that communicates with the rectangular portion. Extending from the upper end of the chamber 14-15, at an acute angle to the axis of chamber 14-15, is an air inlet passageway 22 which has its outer opening spaced a short distance from the top of the burner body and from a thermocouple sensor 23. The sensor is mounted in a stepped diameter passageway formed by outwardly struck portions 24 and 25 and is held in these portions by means of an annular nut 26 threaded into the lower end thereof.

Extending upwardly from the sheet metal portion 13, as an integral extension 13a thereof, is a target-type of burner head having an inverted channel-shaped-portion 27 extending at substantially a right angle from the plane of the sheet metal portions 12 and 13, for directing a flame toward a main burner, when the pilot burner is mounted thereon. Also extending substantially at a right angle to the portion 27 and to the axis of the flame sensor 23, so as to direct a flame thereon, is an inverted channel-shaped portion 28. A downwardly struck wall 29 closes the inner end of the channel-shaped portion 28 and forms a flame divider wall or baflie that cooperates with the rectangular outlet adjacent the portion 200 and the square outlet adjacent the beveled edge 2011. At normal and high gas pressures, gas will flow from the orifice member 16, past the inner end of the air inlet 22, which inspirates air downwardly through said passageway, and causes the mixture of gas and air to pass through the rectangular and square openings at the top of the burner body and to impinge on the target portion 27 and 28. This produces a flame pattern as shown in FIG. 7 of the drawing. Should the gas pressure fall low enough as to provide an insufficient flame for igniting the main burner, all of the gas-air mixture will switch to follow the burner passageway in line with the target 27 and through the rectangular outlet to impinge on the target 27. This flow will support a flame in the direction of the main burner which is large enough to ignite the main burner but causes the flame on the target 28 to become extinguished, which results in the flame sensing thermocouple to become deenergized and to cause a safety valve connected thereto to close.

This switching action takes place as a result of the fluidics phenomenon called Coanda or Wall effect.

This action results from the orifice jet becoming more laminar as a result of reduced inlet pressure. Since the jet is biased to impinge on one surface, it experiences the Coanda effect at low pressures. At normal and high pressures the orifice jet becomes turbulent and the Coanda eflect is defeated or greatly diminished and the gas-air mixture fills both target portions 27 and 28.

It is thus seen that the pilot burner when installed in a heating system, with the invention mounted on a main burner and with the flame sensor connected to a gas safety valve, the burner will provide the proper flames ot ignite the main burner and keep the safety valve open so long as the gas pressure is normal, higher than normal and only slightly below normal pressures; but will cause the safety valve to close before the gas pressure drops to a level which will not support a sufficiently large flame to ignite the main burner, by causing the flame on the sensor to snuff out, while still maintaining a flame that would ignite a main burner to assure that no unburned gas accumulates in the installation.

The embodiments of the invention in which an exclusive property or right is claimed are defined as follows:

1. A pilot burner for a pilot burner-flame sensor combination, comprising a target-type of burner head having an inverted channel-shaped first portion for directing a flame toward a main burner, an inverted channel-shaped second portion having one end adjoining one end of said first portion and extending in a direction at an angle to the first portion for directing a flame onto a flame sensing means, a body portion having a large diameter passageway with its axis substantially at a right angle to and in alignment with the axis of said first channelshaped portion and a narrowed passageway extending toward but short of said burner head channel-shaped portions and having one side wall generally parallel to the axis of said large diameter passageway and a second side wall inclined at an acute angle to said axis, the portion of said passageway opposite said first channel-shaped portion being necked-down at its upper end along the axis of said first channel-shaped head to provide a generally flattened opening connecting with a wider opening opposite said second channel-shaped portion, and means associated with said burner body for supporting a flame sensor in alignment with said second channel-shaped portion.

2. A pilot burner as defined in claim 1 wherein said angle between said portions is substantially a right angle.

3. A pilot burner as defined in claim 1 wherein said second channel-shaped portion is wider than said first channel-shaped portion.

4. A pilot burner as defined in claim 1 wherein a primary air inlet passageway extends from said large diameter passageway adjacent said narrowed passageway extension to the outer edge of said burner body near the top thereof and opposite the means for supporting a flame sensor, .and orifice means in said burner body for directing a stream of gas past said primary air passageway into said narrowed passageway extension.

5. A pilot burner as defined in claim 1 wherein said channel-shaped portions are separated by a wall portion between their adjacent ends. I v

6. A pilot burner as defined in claim 1 wherein said body portion is made of two sheets of metal and said burner head is an extension of one of said sheets.

References Cited UNITED STATES PATENTS CARROLL B. DORITY, JR., Primary Examiner US. Cl. X.R. 136-217 

